2F). Abdominal loop of website III of the envelope protein that is poorly accessible in the mature virion. Rabbit Polyclonal to RBM16 2H12 neutralization assorted between dengue serotypes and strains; in particular, dengue serotype 2 was not neutralized. As the 2H12 binding epitope was conserved, this variance in neutralization shows variations between dengue serotypes and suggests that significant conformational changes in the disease must take place for antibody binding. Remarkably, 2H12 facilitated little or no enhancement of infection. These data provide a structural basis for understanding antibody neutralization and enhancement of illness, which is vital for the development of long term dengue vaccines. Intro Dengue is definitely a mosquito-borne illness of the tropics and 4-HQN subtropics (1, 2). Some 2.5 billion people are at risk and 50-100 million 4-HQN are infected annually. Most infections are either asymptomatic or result in dengue fever (DF2), a relatively mild illness. However, a much more severe form, dengue haemorrhagic fever (DHF3), evolves in 1-5% of infections; this can be life threatening. The incidence of dengue is definitely increasing at an alarming rate and epidemics can seriously disrupt healthcare systems in developing countries (1, 2). Although treatment offers reduced the mortality rate, there is still an urgent need for a vaccine. Dengue viruses have been divided into four serotypes differing in overall amino acid sequence by 30% 4-HQN or more (3, 4). Illness with one serotype does not give life long safety against the additional serotypes (5), and a hallmark of dengue illness is definitely that DHF is definitely more likely to occur following a secondary infection having a heterotypic serotype, rather than following a main illness (6). Halstead proposed antibody-dependent enhancement to explain this paradox whereby an acquired humoral response to the 1st virus could travel a more severe clinical end result upon a secondary exposure (7, 8). There is now good evidence that cross-reactive poorly neutralizing antibodies can travel illness of Fc receptor-bearing cells, such as monocytes, leading to increased illness and virus production (7-12). Dengue disease offers three structural proteins; capsid (C) that encloses the positive strand genome; precursor membrane protein (prM) and envelope (E), both of which are components of the virion envelope structure. Antibodies to prM are generally poorly neutralizing but potent enhancers of illness (13, 14), whereas antibodies against E display more potent neutralizing activity (15-17). E is composed of three domains (ED): I-III4 (18). EDI and EDII are created by discontinuous folds in the membrane proximal N-terminus of the protein; EDII contains the fusion loop. Antibodies that target the highly conserved fusion loop are usually flavivirus cross-reactive (19, 20) but, due to the epitopes inaccessibility on infectious virions, they mostly bind with low avidity and show fragile neutralization (20). Recently, however, a flavivirus cross-reactive mAb 2A10G6 that binds to a newly identified epitope within the fusion 4-HQN loop was shown to be broadly cross-neutralizing and cross-protective (21). EDIII is definitely thought to be involved in sponsor cell connection (22-24), binding to heparan sulfate (25) and/or additional as yet poorly characterized receptor(s) (24). In mice, monoclonal antibodies specific to EDIII are potent neutralizers of dengue disease (26-35), and neutralize more strongly than EDI- or EDII-specific antibodies (33). As a result, EDIII has been considered as a potential immunogen for fresh subunit vaccines (36-40). EDIII is definitely a target of both serotype-specific (16, 26, 27, 32-34, 41, 42) and dengue cross-reactive (28, 30-34, 43) neutralizing antibodies, though the latter tend to neutralize more weakly (28, 34). Here we statement a mouse monoclonal antibody 2H12 that cross-reacts with the four serotypes of the dengue group and which neutralizes Den1, 3 and 4. Crystal constructions of 2H12 Fab with recombinant EDIII were 4-HQN identified at resolutions of 1 1.7 ?, 1.8 ? and 3.0 ? for Den1, Den3 and Den4, respectively. They display the antibody has a conserved mode of binding and contacts a highly conserved epitope in the Abdominal loop of EDIII, which is largely.